include<stdio.h>

int main(){
int mon;
while(scanf("%d",&mon)!=EOF){
int a[1000];
int i,j,k;
a[0]=1;
a[1]=1;
a[2]=2;
a[3]=a[2]+a[0];
for(i=3;i<mon;i++)
a[i]=a[i-1]+a[i-2];
printf("%d\n",a[mon-1]);
}
}